A pipe plug is any type of physical barrier that effectively stops the flow of oil from an oil well or fluid from a pipe. Effective pipe-plugging methods and apparatuses are required in a variety of situations.
Many states regulate the plugging of abandoned well structures to confine oil, gas, and water in the strata in which they are found and prevent them from escaping into other strata and destroying wildlife and water and creating other environmental hazards. It is important in these situations to completely and permanently stop the flow.
When pipelines are damaged, it is necessary to quickly stop the uncontrolled flow, often without regard to the continuing viability of the pipeline. The Deepwater Horizon oil spill (commonly known as the “BP oil spill”) was the largest oil spill in the history of the petroleum industry. An estimated 53,000 barrels per day (8,400 m3/d) escaped from the well just before it was capped, amid an international outcry. Millions of television and Internet viewers watched black plumes of oils spilling into the ocean as the company attempted to inject “dead weight” in the form of heavy liquid and cement and other barriers into the top and bottom of the well.
Inserting a device into the escaping flow was difficult or impossible to control and the dead weight did not prevent blow out causing oil escape at other locations. In addition, due to extremely harsh environments (e.g., ocean floor), repairing these pipes is often very difficult.
Even more controversial than the escaping oil was the inability to monitor the flow of oil while repairs were being made.
Although the Deepwater Horizon oil spill was a well-publicized historic event, damage to pipelines occurs with some regularity and even predictability. Containing the BP spill was the predominant concern without regard to the future viability of the well. Many pipelines, however, must be repaired and placed back into use.
Dead weight plugging methods known in the art generally do not seal the pipes completely. In addition, these plugs cannot be removed once they are in place.
It is necessary to stop or meter the amount the flow during, and possibly after, the repair process. In addition, the plugging device must be capable of being opened or removed from the pipe once the repairs have been completed.
Various plugging methods and apparatuses are disclosed in the art (e.g., U.S. Pat. Nos. 2,646,845, 2,672,200, 2,710,065, 2,969,839, 3,070,163, 3,079,997, and 3,489,216). Invariably, these methods require placement of some type of material (e.g., heavy liquids, gravel, cementitious material, epoxy resin mixture, sealant, drilling mud) to form a solid barrier. These plugging methods and apparatuses are difficult or impossible to remove once the repair has been completed.
Typically, the pipe can be placed back into use only if a section of the pipe is cut out and the device removed. In addition, inserting a device that requires back-filling is complicated as constant pressure has to be applied while the back-filling material is drying.
The prior art also discloses attempts to create plugs which are mechanically adjustable to allow reuse of pipes after a repair. U.S. Pat. No. 6,241,424 (Bath '424) teaches a plug apparatus which includes a body shaft having an external surface and an internal cavity. A cup seal is mounted to the body shaft and engages an interior wall of the pipeline. The cup seal is roughly the size of the internal pipe. A cam is attached to the external surface of the body shaft and a slip assembly slides on the cam to engage a slip with the interior wall. A control mechanism controls the engagement and release of the slip from the interior wall. The plug taught by Bath '424 is not desirable because the fixed diameter of the cup seal does not allow for metered flow.
It is desirable to have a pipe plug which does not require back-filling.
It is desirable to have a pipe plug which may be easily removed from the pipe or which allows for flow through after repairs are made.
It is further desirable to have a pipe plug which allows for controlled and metered flow.